1. Field of the Invention
The present invention relates to a motion vector detecting apparatus for detecting a motion vector of an image and a motion vector detecting method used by the motion vector detecting apparatus, and an image signal processing apparatus for generating a motion-compensated frame by using the motion vector and an image signal processing method used by the image signal processing apparatus.
2. Description of the Related Art
If a video is displayed on an image display device using a liquid crystal panel, a motion blur is easily generated. Thus, in order to improve a video characteristic by reducing a motion blur, the number of frames is increased by interpolating a compensated frame between real frames of an image signal. For example, an image is displayed by converting a frame rate having a vertical frequency of 60 Hz to double, i.e., 120 Hz, or more. A frame rate converting apparatus for converting a frame rate of an image signal detects a motion vector of an image, generates a compensated pixel by using the motion vector, and generates a compensated frame serving as a motion-compensated frame interpolated between real frames.
An image signal includes an image signal in which 24 (24 Hz) frames per second (fps) is converted into 60 fps as in a film image of a movie. In this case, a 2-3 pulldown conversion of converting 24 fps (24 Hz) into 60 fps is used, wherein the 2-3 pulldown conversion is performed by sequentially repeating a process of continuing one cut of a film image for three frames, continuing the next cut for two frames, and then continuing the next cut for three frames. Thus, an image signal of which a frame rate is converted into a vertical frequency of 60 Hz by the 2-3 pulldown conversion does not have smooth motion, and this state is referred to as film judder.
Accordingly, a film judder removing apparatus for removing film judder to form an image signal having smooth motion by generating a motion-compensated frame using a plurality of real frames and a motion vector and by replacing the real frames by the motion-compensated frame is used. A method of removing film judder through a film judder removing apparatus and increasing a frame rate through a frame rate converting apparatus is also used.
Recently, stereoscopic image technology (three-dimensional (3D) image) is spreading rapidly, and thus, a 3D image signal is supplied to an image signal processing apparatus such as a frame rate converting apparatus or a film judder removing apparatus. A format of the 3D image signal includes a format in which an image for a left eye and an image for a right eye are compressed and aligned in a horizontal direction or a vertical direction in one frame. In this case, a left-eye image signal and a right-eye image signal are compressed to half in a horizontal direction or a vertical direction, respectively, and thus, a detection precision of a motion vector is decreased. If a 3D image signal is a pulldown-converted image signal, a distance in which an image moves in one frame is increased, and thus, the detection precision of the motion vector is further decreased.
As such, if an image signal is a pulldown-converted 3D image signal through pulldown conversion, it is difficult to detect a motion vector with high precision. Accordingly, in an image signal processing apparatus for generating a motion-compensated frame, a wrong compensation may easily occur, and image quality of the motion-compensated frame may deteriorate.
3. Prior Art Reference
(Patent Reference 1 Japanese Laid-Open Patent Publication No. 2009-200802